Convection and radiation heat transfer in a tube with core rod and honeycomb network inserts at high temperature

Abstract

Heat transfer and friction factor characteristics in a circular tube fitted with core rod and honeycomb network inserts at high temperature have been investigated experimentally. In the experiments, ambient air with Reynolds numbers ranging from 6000 to 20,000 is passed through a circular tube with uniform wall temperature. Convection and radiation heat transfer phenomena are studied. The experimental results show that at uniform wall temperatures of 373, 473, 553, and 633 K, the average shares of the radiation heat transfer coefficient to the total heat transfer coefficient are 13.9%, 18.3%, 24.7%, and 28.7% for core rod and 11.5%, 13.1%, 15.3%, and 17.8% for honeycomb network insert, respectively. In addition, the heat transfer coefficient increased by 227%, 299%, 327%, and 369% for core rod and 409%, 529%, 614%, and 679% for honeycomb network insert compared with the plain tube under the aforementioned temperatures.